Spurge, a name given to many plants in the Euphorbia genus, is a diverse group found across the globe. These plants are often encountered as persistent, low-growing weeds that aggressively colonize lawns, gardens, and sidewalk cracks, making them a common nuisance. Spurge species are known for their rapid spread and resilience. Understanding the nature of this pervasive weed is the first step toward effective management.
Defining the Spurge Family (Euphorbia)
Spurge belongs to the botanical family Euphorbiaceae, which includes over 7,000 species, but the term “spurge” most commonly refers to plants within the genus Euphorbia. This genus is one of the largest and most varied groups of flowering plants, encompassing everything from small annual weeds to large, woody trees and desert succulents.
Despite their physical differences, all plants in the Euphorbia genus share a unique floral structure called a cyathium. This specialized inflorescence mimics a single flower by combining highly reduced male and female flowers within a cup-like arrangement of fused bracts. The structure typically includes one central female flower surrounded by multiple male flowers. Another defining characteristic shared by almost all members is the presence of a milky, white sap or latex, which is exuded when the plant is damaged.
How to Identify Common Spurge Varieties
The most common nuisance varieties in landscapes are annual weeds like Spotted Spurge (Euphorbia maculata) and Prostrate Spurge (Euphorbia humistrata), which thrive in thin, compacted soil. Spotted Spurge has a prostrate, mat-forming growth habit, with stems radiating out from a central taproot. Its small, oval-shaped leaves are arranged oppositely and often display a distinct red or purple spot in the center.
Prostrate Spurge is difficult to distinguish from Spotted Spurge, as both grow low to the ground and possess small leaves. A key difference is that Prostrate Spurge may develop roots along the stem nodes where they touch the soil, while Spotted Spurge typically does not. Leafy Spurge (Euphorbia esula), in contrast, is a perennial variety that grows upright, reaching up to three feet tall, and is characterized by narrow, alternate leaves and a persistent, deep root system.
The Toxic Nature of Spurge’s Milky Sap
When a spurge plant’s stem is broken or damaged, it releases a white, sticky substance known as latex, which is the source of the plant’s toxicity. This latex contains irritating compounds, primarily diterpene esters, which act as a defense mechanism against herbivores. Direct contact with this milky sap can lead to adverse health effects in humans and pets.
Skin exposure to the sap is common and can result in contact dermatitis, causing redness, swelling, and sometimes blistering. If the sap is inadvertently transferred to the eyes, it can cause severe irritation, blurred vision, and may even lead to temporary blindness if not promptly treated.
Ingestion of the plant material can cause painful local irritation of the mouth and throat, excessive salivation, and gastrointestinal symptoms like vomiting and diarrhea. Washing the exposed skin with soap and water immediately is important, as rinsing with water alone may not fully remove the irritating compounds.
Methods for Removal and Prevention
Managing spurge effectively requires a combined approach that addresses both existing plants and the prevention of future germination.
Manual Removal
For small, isolated patches, manual removal is the most straightforward method, provided the entire taproot is extracted to prevent regrowth. It is important to wear gloves and eye protection during any hand-pulling to avoid contact with the toxic sap.
Cultural Control
Cultural control methods focus on creating an environment where spurge cannot thrive, as the weed prefers thin turf and compacted, dry soil. Maintaining a healthy, dense lawn through proper watering, fertilization, and mowing will naturally crowd out spurge and reduce bare soil spots. Applying a heavy layer of mulch in garden beds can also suppress germination by blocking sunlight.
Chemical Control
For widespread infestations, chemical controls may be necessary, involving the use of selective herbicides. Pre-emergent herbicides can be applied in the early spring to create a barrier that prevents spurge seeds from germinating. For established plants, a selective post-emergent herbicide labeled for spurge control can be spot-treated directly onto the weeds.